A conventionally known image forming apparatus is configured as follows. A developer is supplied in such a manner that the developer is uniformly distributed on the circumferential surface (developer carrying surface) of a rotatively driven developing roller without involvement of contact between the developing roller and developer supply members, such as a supply roller. A portion of the developer adhering to the circumferential surface of the developing roller adheres to the circumferential surface (latent image forming surface) of a latent image carrying body on which an electrostatic latent image is formed, at positions corresponding to the electrostatic latent image. An image in the developer adhering to the latent image forming surface is transferred onto paper, whereby the image is formed on the paper.
Such an image forming apparatus is disclosed in Japanese Patent Application Laid-Open (kokai) No. 3-12678. The disclosed image forming apparatus includes an upstream transport surface and a downstream transport surface. While facing the circumferential surface of the developing roller, the upstream transport surface is disposed upstream, with respect to the rotational direction of the developing roller, of a predetermined developing area where the circumferential surface of the developing roller and the latent image forming surface are in proximity to each other. While facing the circumferential surface of the developing roller, the downstream transport surface is disposed downstream of the developing area with respect to the rotational direction of the developing roller. In the image forming apparatus, electric fields for moving a charged developer from the upstream side toward the downstream side with respect to the rotational direction of the developing roller are formed in a space on the upstream transport surface and in a space on the downstream transport surface. By this procedure, the charged developer moves on the upstream transport surface and on the downstream transport surface, from the upstream side toward the downstream side with respect to the rotational direction of the developing roller.
When the developer is transported on the upstream transport surface, the developer disperses from the upstream transport surface toward the circumferential surface of the developing roller. As a result, the developer which has reached the circumferential surface of the developing roller adheres to the circumferential surface. In the image forming apparatus, the developing roller is not in contact with developer supply members; thus, it is possible to prevent the developing roller from being damaged due to friction or the like.